1. Field of the Invention
The invention relates to a carbonaceous material, to a process for the production thereof and to the use thereof.
2. Description of the Related Art
There exist many known processes used for the production of derivatized carbonaceous materials. These processes typically involve using derivitization reagents or conditions that are generally considered disadvantageous. Such pitfalls include, but are not limited to; instability and toxicity of derivitization reagents needed to effect such reactions. Furthermore, these reagents present handling problems, as they can undergo uncontrollable decomposition during the course of the reaction. In many instances, strongly acidic media must be used; thereby necessitating the use of special reaction vessels. The following disclosures are of interest to the instant invention, as they possess some of the disadvantages mentioned herein.
EP 0569503 discloses a process for surface-modifying carbonaceous material with aromatic groups by electrochemical reduction of a diazonium salt.
It is furthermore known to provide carbonaceous material with organic groups by coupling the organic groups with the carbonaceous material by diazotization (WO 96/18688).
It is further known to provide carbonaceous material with organic groups by binding the organic groups to the carbonaceous material by means of reactions with free-radical formers (Ohkita K., Tsubokawa N., Saitoh E., Carbon 16 (1978) 41); DE 10012784.3) or by cycloaddition reactions (DE 10012783.5).
It is known to react carbonaceous material with aliphatic compounds which have azo groups (JP11315220 A; Tsubokawa N., Kawatsura K., Shirai Y., Int. Conf. Mater. Proc. 11 (1997) 537; Tsubokawa N., Yanadori K., Sone Y., Nippon Gomu Kyokaishi 63 (1990) 268). The bond is formed between the compounds containing azo groups and the carbonaceous material with elimination of nitrogen and formation of free-radical species, which may act as starter functions for further reactions (grafting).
It is likewise known to modify carbonaceous material by reaction with sulfuric acid or SO3 (U.S. Pat. No. 3,519,452; JP 2001-254033).
There exist other known processes that have known disadvantages, which are noted as follows. It is known that the commonly employed oxidizing substance sodium nitrite is toxic, but the nonionic organic nitrites also used for diazotization are toxic and highly combustible as well. The resultant by-products of the organic nitrites (e.g., counterions, alkyl residues) become incorporated within the confines of the carbonaceous material as contaminants.
Another type of problem encountered while using nitrites is that the diazotization reaction occurs in an acidic medium, which may result in the formation of toxic nitrogen oxides.
Another issue of concern is the utilization of free-radical formers that are thermally or photochemically labile, and as a result possess explosive tendencies. This aspect gives rise to substances that may give rise to chain reactions that are difficult to control. Compounding this problem is found in the fact that the synthesis and purification of the corresponding precursors of the free-radical formers, in some cases, involve substances that are toxic or are unpleasantly odoriferous; which typically means that they are costly with regard to the production process, transport, use and ultimate disposal.
Yet another complicating issue is that cyclization reactions involving nitrogen-heterocycles gives rise to nitrogen extrusion during the course of the conversion from reactants to products, which may result in sudden, explosive expansions in volume or increases in pressure, which substantially complicate reaction control.
Additionally, the reaction of carbonaceous material with compounds which have azo groups can form free-radicals with concomitant nitrogen extrusion, and may likewise result in sudden, explosive expansions in volume or increases in pressure, or alternatively in chain reactions which are difficult to control thermally and so complicate reaction control.
As mentioned above, the reactions, in many instances, must occur within acidic media; thereby requiring that the reaction vessels be constructed from particularly stable, corrosion- and temperature-resistant materials. When carbonaceous material is reacted in the presence of either sulfuric or fuming sulfuric acid, unwanted and hazardous oxidations may occur as secondary reactions. These strongly acidic media require neutralization at the conclusion of the reaction; wherein said neutralization produces a large amount of wastewater and increases the overall salt content of the media, which subsequently may be incorporated into the carbonaceous material, which, in turn, may lead to applicational disadvantages.
Accordingly, it is an object of the present invention to overcome these disadvantages by producing a carbonaceous material with organic groups, wherein: (1) modification of the carbonaceous material is variable in such a manner that the functional groups may be close to and/or very distant from the surface; (2) modification of the carbonaceous material proceeds without upstream reactions, such as activation with starters; (3) the reactions with the modifying agents according to the invention proceed purely thermally and no further catalysts (for example Lewis acids) or other activation variants, such as for example photochemical processes, are required; (4) due to the chemical properties of the modifying agents according to the invention, no disruptive secondary reactions or difficult to control chain reactions can occur; (5) the resultant carbonaceous material is not contaminated by acids, salts and the like, such that no purification of the carbonaceous material is necessary; (6) the carbonaceous material does not need to be dried with an elevated energy input; (7) no toxic waste gases arise during the modification; (8) no or only small quantities of readily removable solvents are necessary.